Well ladies and gentlemen, it looks like the summer heat is here once again! If you’ve been reading Trees Full of Money for a while, you’re probably aware of how passionate I am about the use of geothermal energy to heat and cool your home. Using energy stored in your own back yard, Geothermal Heat Pumps can save consumers 70% or more on their yearly heating and cooling bills, and best of all ground source heat pumps have a minimal impact on the environment.

Traditional Geothermal Heating and Cooling Systems are Expensive

Unfortunately, the cost of a professionally installed geothermal system is prohibitive to most homeowners. Complete residential geothermal systems can cost $20,000 to $30,000 or more depending on the application.

My Do It Yourself Alternative

Until such time that geothermal systems become less expensive (or I get a significant windfall of cash) I would like to share my tips on an alternative way to harvest geothermal energy to “partially” cool your home during those sweltering summer days.

This method has been utilized by many homeowners in the northern states for years without them ever realizing that they were tapping into a source of renewable energy. I have simply “perfected” the process to get the most efficient use out of the cool air that is stored inside your home’s basement.

If your home doesn’t have a basement or suitable crawl space beneath it, you will not be able to utilize this technique but you may be interested in reading about it anyway.

What Equipment You Need for My DIY Geothermal Cooling System:

A “Below Ground” basement or crawl space with direct access from inside your home (it also helps if your basement or crawl space has a small window that can be opened to add air flow).

A Portable Fan.

Optional: A Portable Dehumidifier

Why My DIY Geothermal Cooling System Works

During hot summer days and cold winter nights, basements in our homes stay relatively mild when compared with the outside temperatures and the temperatures in the main part of your house. This is a classic example of how geothermal energy works.

The temperature of your basements exterior walls are regulated by the relatively constant temperature of the radiant heat trapped only a few feet down beneath the ground adjacent to your home’s foundation walls. These temperatures radiated through your basements walls and cool (or heats) the air volume inside your basement. The trick is getting this usually damp and musty cool air distributed throughout the rest of your home.

After some experimenting, I have finally come up with the most efficient method for achieving this goal.

Setting Up My Do It Yourself Geothermal Cooling System

I place a small dehumidifier in my basement the night before to bring the relative humidity down from over 80% to less 60% by the following morning. I also ensure that all of the window shades are drawn on the “sunny side” of my house to minimize the effect of the suns “solar” heating. If your has a relatively low humidity then the use of a dehumidifier may not be necessary.

If the outside temperature gets below 75deg during the night I will leave most of the upstairs windows open in my house with fans sucking in the “cool” air until the outside temperature gets above this level.

As the sun comes up and the inside temperature of the house begins to rise I wait until the inside temperature of the house gets above 77deg. At this point I “turn on” my geothermal system by doing the following:

I crack open one of the small windows in my basement just enough to let a little bit of airflow through. Then (with all of the other windows closed in the house) I crack open another window in one of my homes upstairs bedrooms with all doors open between the two windows so that air can flow through (tip: opening the highest window you have in your home will vent out the most hot air in your home [heat rises!]). You can also close of other areas of the house that you do not wish to cool to maximize the cooling effect in the areas of the house you frequent during the day.

I then place a small window fan in an upstairs window with the flow of air pointing out the window. This technique effectively suck air up from the basement through the house and then out the window.

The trick is to monitor the temperature of the air on the suction side of your fan as it is being pushed outside. Close the windows (and the basement door) and shut the fan down when the drop in the rooms temperature begins leveling off.

It usually takes between 30 minutes to an hour for all of the cool air to be circulated through depending on your fan’s power and how large your home is. If all has gone to plan, the temperature inside your home should have dropped a more tolerable 4-5 degrees. This may buy you a couple of hours time that you don’t need to run your air conditioner.

Caution: If you run the fan too long, all of the cool air that was trapped in your basement will be displaced by the warmer outside which will then be sucked up into the rest of your home negating the whole process. You generally only get one shot at this cool air during the day since it will take at least 6 hours for your cool basement walls to regulate the temperature of the new mass of warm air that has been displaced into your basement.

It may seem like a lot of work but you really get the hang of it after a weekend of testing and if nothing else this DIY geothermal energy project is a fun experiment to share with your family! Thanks for reading and be sure to check out some of my other articles on personal finance, and alternative energy! I am also curious to hear how this technique works for you, be sure to comment below with any successes, failures, or criticisms of this method!

48 Responses

It’s my understanding that a dehumidifier is simply and Air Conditioner that heats back up the air. As such, it would be smarter to run an AC than a dehumidifier. With that understanding, it would make sense to run the AC in the hottest part of your house at night.

It might cost the same and you’d get a cooler room. Then again, maybe I’m totally wrong — certainly worth testing. Just be sure to use a window AC unit or at least one that vents hot air outside. There are units sold now that cool one room while heating the other which is lame. You can tell those because they don’t have two vents, one for intake and one for exhaust.

richard.2 years ago

i would think that by simply cooling and reusing the exhaust air from the house, you would be building up the carbon dioxide levels in the house. not good.

You’re not reusing exhaust air. You’re bringing in fresh air from the outside of the house into the basement. From their the air is cooled (by the basement’s geothermal properties) and then pulled through the house and out the window again.